Thermally protected switches of the general type described above are known and are available in commerce. In switches of this type, the switch housing is constructed of two separate parts, i.e., a surrounding housing shell and a cover or lid. In other instances, the switch is composed of two housing shells which are permanently joined together after assembly of the internal switch elements, for example by riveting, welding, gluing or by a non-releasable snap connection. When this type of housing is sealed, it is thereafter impossible to engage internal elements of the switch for the purpose of adjustment or calibration without damaging a part of the housing or without tedious removal of the rivets which hold the housing parts together. On the other hand, the switch mechanism cannot be adequately tested prior to assembly nor can it be calibrated because the switch mechanism depends on numerous interacting and load-bearing elemens which are part of the housing and are not available to the switch mechanism until it is fully assembled.